In copending, commonly assigned continuation-in-part application Ser. No. 945,842, filed on Sept. 26, 1978, there is disclosed a master-follower light regulator system which is designed to utilize daylight and overcome other disadvantages of conventional fluorescent lamp systems, as well as to reduce the amount of electrical energy used to provide fluorescent lighting in buildings and the like. The basic component of the system is an electronic regulator in each fixture which is equipped to adjust to the ambient lighting.
The application discloses that a second or subsequent fixtures can be controlled by a master, or in the case of a plurality of fixtures, either by the master or a preceeding fixture. The application also contains a discussion of the problem of controlling the light output of fluorescent lamps operating from more than one inductive ballast. In brief, where it is desired to control the light output of two or more separately ballasted units containing pairs of lamps without paying the substantial economic penalties associated with providing a separate control system for each unit, certain problems must be overcome. Specifically, two ballasts cannot be operated in parallel from a single control system because the lamp pairs act in such a manner that only the pair that first reaches the arc discharge region is actually controlled. As a solution to this problem, the application discusses the provision of a conductive coupling from the emitter of a control transistor of a ballast control device, which coupling is used as a control input for controlling the primary current of the inductive ballast of the follower unit. Moreover, the application in question provides for the use of electro-optical devices to eliminate the wiring employed in the conductive coupling between the master units.